X-ray CT (Computed Tomography) systems are a type of equipment that provides imaging of the interior of a subject by scanning the subject with X-ray equipment for data acquisition and then by processing the data with a computer.
Specifically, an X-ray CT system irradiates the subject with X-rays multiple times in different directions, detects the X-rays that have passed through the subject with an X-ray detector, and acquires multiple sets of detection data. The detection data gathered are A/D converted by a data acquisition system and then transmitted to a console device. The console device performs preprocessing on the detection data and thereby generates projection data. Then, the console device executes reconstruction-processing on the projection data and generates volumetric data based on a set of tomographic data or a plurality of sets of tomographic data. Volumetric data are a data set representing a three-dimensional distribution of CT values that corresponds to a three-dimensional area in the subject.
The X-ray CT system can display an image in an MPR (Multi-Planar Reconstruction) view by rendering the volumetric data in a given direction. In the following descriptions, the sectional images that are MPR views achieved by rendering the volumetric data are also referred to as “MPR images”. MPR images are, for example, axial images, which are sections slicing the subject at a right angle to the axis of the body, sagittal images, which are sections slicing the subject vertically along the body axis, and coronal images, which are sections slicing the subject horizontally along the body axis, (these three types are sometimes collectively referred to as “three-orthogonal-axis images”). Furthermore, MPR images include views in arbitrary sectional planes passing through the volumetric data (oblique images) and curved MPR images. Curved MPR images are views in curved sectional planes, for example, sectional views along the coronary arteries of the heart, and along the jawbone or the dentition. A plurality of MPR images created in such conditions can be displayed simultaneously on a display unit, etc.
There is a scanning method called CT fluoroscopy (CTF: Computed Tomography Fluoroscopy), which is performed using an X-ray CT system. CT fluoroscopy is a method of scanning in which X-rays are continually radiated on the subject to acquire real-time images of a region of interest in the subject. In CT fluoroscopy, the rate of detection data gathering is set low to shorten the time required for reconstruction-processing, so that images are displayed in real time. CT fluoroscopy is applied to monitoring, for example, positional relations between the leading end of the puncture needle and the site where a tissue sample is to be collected during biopsy or to monitoring the position of the tube in draining methods. By the way, draining methods are a type of procedure for draining, with a tube, bodily fluids that have accumulated in body cavities.
In a case where a biopsy is performed on the subject while MPR images based on the volumetric data acquired by CT fluoroscopy are being referred to, for example, scanning and puncturing are executed repeatedly one after the other. Specifically, at first, an MPR image of the subject is acquired by CT fluoroscopy, and a doctor or the like performs puncturing while the MPR image is being referred to. In the puncturing procedure, when puncturing has been executed to a certain extent, CT fluoroscopy is performed again, for example, to check the positional relation between the leading end of the puncture needle and the site where a tissue sample is to be collected. The doctor or the like proceeds with the puncturing further by referring to the MPR image created on the basis of this newly performed CT fluoroscopy. These actions are repeated until the biopsy is completed, for ensuring accurate biopsy.